In Vitro fermentation of oat and barley derived β-glucans by human faecal microbiota.
Hughes, S. A., Shewry, P. R., Gibson, G. R., McCleary, B. V. & Rastall, R. A. (2008). FEMS Microbiology Ecology, 64(3), 482–493.
Fermentation of β-glucan fractions from barley [average molecular mass (MM), of 243, 172, and 137 kDa] and oats (average MM of 230 and 150 kDa) by the human faecal microbiota was investigated. Fractions were supplemented to pH-controlled anaerobic batch culture fermenters inoculated with human faecal samples from three donors, in triplicate, for each substrate. Microbiota changes were monitored by fluorescent in situ hybridization; groups enumerated were: Bifidobacterium genus, Bacteroides and Prevotella group, Clostridium histolyticum subgroup, Ruminococcus-Eubacterium-Clostridium (REC) cluster, Lactobacillus-Enterococcus group, Atopobium cluster, and clostridial cluster IX. Short-chain fatty acids and lactic acid were measured by HPLC. The C. histolyticum subgroup increased significantly in all vessels and clostridial cluster IX maintained high populations with all fractions. The Bacteroides-Prevotella group increased with all but the 243-kDa barley and 230-kDa oat substrates. In general β-glucans displayed no apparent prebiotic potential. The SCFA profile (51 : 32 : 17; acetate : propionate : butyrate) was considered propionate-rich. In a further study a β-glucan oligosaccharide fraction was produced with a degree of polymerization of 3-4. This fraction was supplemented to small-scale faecal batch cultures and gave significant increases in the Lactobacillus-Enterococcus group; however, the prebiotic potential of this fraction was marginal compared with that of inulin.
In vivo effects of dietary (1→ 3),(1→ 4)-β-D-glucans from oat on mucosal immune responses in man and mice.
Volman, J. J., Mensink, R. P., Buurman, W. A. & Plat, J. (2011). Scandinavian Journal of Gastroenterology, 46(5), 603-610.
Objective. Antimicrobial peptides and tight junction proteins are crucial to maintain mucosal immunity. It is known that oat β-glucan may affect intestinal immunity. Therefore, the aim of the present study was to evaluate the effect of oat β-glucan on the presence of antimicrobial peptides and tight junction protein. Material and methods. We analyzed antimicrobial peptide levels in fecal water prepared from 24 h ileostomic bag contents obtained from ileostomic patients consuming oat β-glucan enriched or control diets in a cross-over design. In addition, intestinal sections of mice, which received oat β-glucan via oral gavages for 3.5 days, were analyzed for lysozyme and zonula occludens-1 expression. Results. We observed a trend toward lower lysozyme (−23%; p = 0.076) and bactericidal/permeability-increasing protein (−17%; p = 0.098) levels in oat β-glucan enriched fecal water as compared with placebo. Additionally, mice receiving oat β-glucan showed a lower lysozyme expression in stained distal small intestinal sections (p = 0.011). Staining of zonula occludens-1 was decreased in β-glucan treated mice indicating disruption of the tight junction integrity. Conclusions. In conclusion, the consumption of oat β-glucan seems to decrease the levels of antimicrobial peptides in fecal water from human ileostomy patients and its expression in distal small intestine sections in mice. The decreased intestinal integrity in mice could be explained by the drop in antimicrobial peptides.
In-vitro assessment of the effects of dietary fibers on microbial fermentation and communities from large intestinal digesta of pigs.
Lin, B., Gong, J., Wang, Q., Cui, S., Yu, H. & Huang, B. (2011). Food Hydrocolloids, 25(2), 180-188.
Dietary fibers (oat β-glucan, flaxseed gum, and fenugreek gum) can be fermented to short chain fatty acids (SCFAs) in batch cultures by pig intestinal digesta. Lactate in the β-glucan-grown cultures had the highest level among SCFAs produced, whereas flaxseed or fenugreek gum-containing cultures generated a significant amount of acetate, propionate and butyrate over three subcultures tested (p< 0.05). Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA genes in the initial and subcultures revealed that types of fibers impacted pronouncedly on the bacterial community structure. Identified DGGE DNA bands were mainly affiliated with Bacteroidetes, and Firmicutes, in which numbers of butyrate-producing species were widely distributed. The fermentability of dietary fibers to SCFAs and their selection towards the bacterial communities suggest their potential application in promoting animal/human health.
Understanding the role of oat β-glucan in oat-based dough systems.
Londono, D. M., Gilissen, L. J. W. J., Visser, R. G.F., Smulders, M. J. M. & Hamer, R. J. (2015). Journal of Cereal Science, 62, 1-7.
Β-glucan is one of the components that differentiate oats from other cereals and that contribute to the health-related value of oats. However, so far oats cannot easily be applied in bread-like products without loss of product quality. Here we have studied how the content and viscosity of oat β-glucan affect the technological properties of oat dough in both a gluten-free and a gluten-containing system. In both systems, increasing the β-glucan concentration resulted in an increase of dough stiffness and in a reduction of dough extensibility. β-glucan negatively impacted the elastic properties that additional wheat gluten conferred to oat dough. This effect was smaller for medium-viscosity β-glucan than for high-viscosity β-glucan. Interestingly, dough made from low β-glucan flour (<2%) had increased gas retention capacity. Overall, the impact of β-glucan on the properties of oat dough systems was governed by concentration and viscosity, with or without additional wheat gluten. Our findings indicate that β-glucan is a key component that determines the rheology of oat-based dough systems and, with that, the technological functionality of oat in dough systems.
Endo-glucanase digestion of oat β-Glucan enhances Dectin-1 activation in human dendritic cells.
Sahasrabudhe, N. M., Tian, L., van den Berg, M., Bruggeman, G., Bruininx, E., Schols, H. A., Faas, M. M. & de Vos, P. (2016). Journal of Functional Foods, 21, 104-112.
Oat β-Glucans were studied for their immunological impact before and after enzymatic digestion in order to enhance the efficacy of oat β-Glucans for application in functional foods. Oat β-Glucan is reported to have minimal impact compared to its fungal counterpart in vitro. Digestion with endo-glucanase enhanced its efficacy towards stimulating MCP-1, RANTES, IL-8, and IL-4 production in human dendritic cells as compared to the nondigested β-Glucan. This effect resulted from an enhanced activation of the Dectin-1 receptor. Our data suggest that the immune-stimulation was dependent on the β-(1-3) linkages and the reduced particle size of digested β-Glucans. Thus, we show that enzymatic pre-digestion of dietary fibres such as oat β-Glucan enhances its impact on specific immune receptors. We also demonstrate that particle size and/or molecular weight of oat β-Glucans and exposure of specific binding sites for the receptors might be important tools for designing efficacious functional feed and food additives.
Influence of oat components on lipid digestion using an in vitro model: Impact of viscosity and depletion flocculation mechanism.
Grundy, M. M., McClements, D. J., Ballance, S. & Wilde, P. J. (2018). Food Hydrocolloids, 83, 253-264.
Depletion flocculation is a well-known instability mechanism that can occur in oil-in-water emulsions when the concentration of non-adsorbed polysaccharide exceeds a certain level. This critical flocculation concentration depends on the molecular characteristics of the polysaccharide molecules, such as their molecular weight and hydrodynamic radius. In this study, a range of analytical methods (dynamic shear rheology, optical microscopy, and static light-scattering) were used to investigate the interaction between lipid droplets and polysaccharides (guar gum and β-glucans) of varying weight-average molecular weight and hydrodynamic radius, and concentration. The aim of this work was to see if the health benefits of soluble fibers like β-glucans could be explained by their influence on the structure and digestibility of lipid emulsions. The apparent viscosity of the emulsions increased with increasing polysaccharide concentration, molecular weight, and hydrodynamic radius. Droplet flocculation was observed in the emulsions only at certain polysaccharide concentrations, which was attributed to a depletion effect. In addition, the water-soluble components in oat flakes, flour, and bran were extracted using aqueous solutions, to examine their impact on emulsion stability and properties. Then, the rate and extent of lipolysis of a sunflower oil-in-water emulsion in the presence of these oat extracts were monitored using the pH-stat method. However, the inhibition of lipolysis was not linearly related to the viscosity of the oat solutions. The water-soluble extracts of β-glucan collected from oat flakes had a significant inhibitory effect on lipolysis. The results of this study increase our understanding of the possible mechanisms influencing the impact of oat constituents on lipid digestion. This work also highlights the importance of considering the molecular properties of polysaccharides, and not just their impact on solution viscosity.